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Search for the U ltra H igh E nergy C osmic R ay Sources : the Current S tatus

Search for the U ltra H igh E nergy C osmic R ay Sources : the Current S tatus. Hang Bae Kim ( HanYang University) High1-2014 KIAS-NCTS Joint Workshop on Particle Physics, String Theory and Cosmology February 12, 2014. Ultra-High-Energy Cosmic Rays. Cosmic Rays

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Search for the U ltra H igh E nergy C osmic R ay Sources : the Current S tatus

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  1. Search for theUltra High Energy Cosmic RaySources : the Current Status Hang Bae Kim (HanYang University) High1-2014 KIAS-NCTS Joint Workshop on Particle Physics, String Theory and Cosmology February 12, 2014

  2. Ultra-High-Energy Cosmic Rays • Cosmic Rays • High energy particle from outer space • Primarily composed of proton & nuclei • Originated from SNe, AGN, … ? • Influence on the life • Ultra-High Energy Cosmic Ray (UHECR) • Energy :1962, E>1020 eV at Vocano Ranch1991, E=3£1020 eV at Fly’s eye(OMG particle) ~ kinetic energy of a baseball with a speed of 100 km/h • Extensive Air Shower (EAS) • Extragalactic origin • Where and How can particles reach such extremely high energies? 1 particle/km2/century

  3. Production • Acceleration of charged particles • Decay of superheavy particles Propagation • Cosmic background(Microwave, Radio wave, Magnetic fields) • Energy loss • Secondary CR production • Deflection and Time lag Observation • Atmosphere as calorimeter / scintillator • Composition • Energy • Arrival Direction

  4. Observation • Detection of EAS • Surface Detector (SD) – e, ¹ • Fluorescence Detector (FD) - UVL • Cherenkov Radiation • Radio wave • Radar reflection • Longitudinal development • Lateral distribution

  5. Pierre Auger Observatory (PAO) Surface Detector – Water Cherenkov 60 km Fluorescence Detector – PMT • Location : Mendoza, Argentina • SD : 1600 water Cherenkov detector, 1.5 km spacing, 3000 km2 • FD : 24 telescopes in 4 stations

  6. Telescope Array (TA) Surface Detector – Plastic Scintillation MD FD station BRM LR SD array Fluorescence Detector – PMT 35km • Location : Utah, USA • SD : 507 plastic scintillation detector, 1.2 km spacing, 678 km2 • FD : 18 telescopes in 3 stations

  7. JEM-EUSO (planned)

  8. Energy, Arrival Direction Surface Detector Energy Calibration through hybrid events Lateral distribution Good energy estimator Signal & Timing S(1000) Distance from the shower axis Fluorescence Detector Longitudinal development

  9. Composition Longitudinal development Shower maximum Xmax, depth of shower maximum atmospheric depth Xmax, the depth of shower maximum depends on energy and compositionof primary CR particle. Average longitudinal development of proton and Fe nucleus obtained from simulation. Proton has larger X_{max} than Fe. Observed variation of Xmax as a function of energy.

  10. Propagation Energy Loss UHECR p, A, γ interact with CMB photons. The energy of protons as a function of the propagation distance. Modification factor of energy spectrum Injected spectrum ! Observed spectrum

  11. Propagation Deflection Magnetic fields ! Deflection and Time lag • Galactic magnetic fieldBG ~ 10-6 GRG~10kpc • Extragalactic magnetic fieldBEG ~ 10-9 – 10-6 G (very uncertain) Proton propagation in a magnetic field of 10-9G

  12. Production Top-down : Decay of superheavy particles, Emission from Topological defects • Superheavy particle with long lifetime • Emission from topological defects • Cosmic origin involves new (cosmology + particle physics) • Signatures of top-down models • Spectral shape – No GZK cutoff, flat spectrum • Composition – Neutrinos and photons are dominant • Arrival Directions– Galactic anisotropy

  13. Production Bottom-up : Acceleration of charged particle at astrophysical sites Maximum attainable energy • Acceleration mechanism • Diffusive shock acceleration • Acceleration site • AGN, GRB, …

  14. Latest Results and Issues Energy spectrum • 1990s, AGASA reported No GZK cutoff. • HiRes, Auger, TA confirmed GZK cutoff. Abu-Zayyad et al. (2013)

  15. Latest Results and Issues Composition HiRes (Abbasi et al. 2010) PAO (Abraham et al. 2010) TA (Tameda et al. 2011) PAO : Transition from proton to heavy nuclei - Ad hoc composition model (p, He, N, Fe) HiRes&TA : Proton

  16. Latest Results and Issues Arrival directions AGASA (Hayashida et al. 2000) HiRes (Abbasi et al. 2008) AGASA - Isotropy with small clustering TA (Abu-Zayyad et al. 2012) PAO (Abreu et al. 2010) • Auger • Anisotropy • Correlation with AGNs • Low (<10^{19} eV) energy isotropy • Above GZK cutoff, anisotropy confirmed PAO – Correlation with AGN

  17. Study of Arrival Directions • Isotropy • Astrophysical Objects Experiment Modeling Simulation Observed AD distribution Expected AD distribution Statistical Comparison • Test Methods - Statistic • Multipole moments, 2D KS, … • KS on the reduced 1D distribution Probability that the observed distribution is obtained from the expected distribution

  18. Exposure Function • The detector array does not cover the sky uniformly and we must consider its efficiency as a function of the arrival direction. • Here we consider only the geometrical efficiency.

  19. Kolmogorov-Smirnov Test • Comparison of two one-dimensional distributions • Kolmogorov-Smirnov statistic Cumulative probability distribution KS statistic Kuiper statistic • Probability that the observed distribution isobtained from the expected distribution Anderson-Darling statistic

  20. RA, DEC Distribution 2D Distribution Observed Data (TA, E≥1 EeV) Simulation Data (Isotropic) 1D Distribution RA Distribution DEC Distribution

  21. Auto-Angular Distance Distr. (AADD) Caution: AADD is not an independent sampling.Probability(D) must be obtained from simulation. clustered isotropic

  22. Correl. Angular Distance Distr. (CADD) H.B.K, J. Kim, JCAP 1103, 006 (2011) correlated isotropic

  23. Super-Heavy Dark Matter (SHDM) Model • UHECR flux is obtained by the line-of-sight integration of the UHECR luminosity function L(R), which is proportional to the DM density ρ(R). • Galactic DM contribution / Extragalactic DM contribution • Galactic DM contribution UHECR Luminosity Dark Matter Profile

  24. Super-Heavy Dark Matter (SHDM) Model Unfavorable

  25. AGN Model H.B.K, J. Kim, JCAP 1103, 006 (2011)IJMPD 22, 1350045 (2013) • Hypothesis : UHECRs are composed of • AGN contribution,fraction fA • Background (isotropic) contribution,fraction 1-fA • Selection of UHECR data • Energy cut • We take • Selection of AGN • Distance cut • We take • Notes • The fraction f depends on Ec and dc. PAO-AGN

  26. AGN Model • UHECR flux from AGNFor simplicity, we assume the universality of AGN. • Expected flux • AGN contributionfraction fA, • Isotropic componentfraction 1-fA, UHECR Luminosity Distance Smearing

  27. AGN Model • Steep rise of CPD near µ=0 means the strong correlation at small angles. • PAO data are not consistent with isotropy, meaning that they are much more correlated with AGNs than isotropic distribution. • PAO data are not consistent either with the hypothesis that they are completely from AGNs. • Adding isotropic component can make the consistency improved. The cumulative probability distribution of CADD using the AGN reference set

  28. AGN Model PAO • Consistent with the simple AGN model when enough isotropic component is added. • Cf. Fiducial value of f

  29. Point-wise Anisotropy • Idea – Sweep the whole sky and perform the point-wise comparison to the isotropic distribution (Comparison method: CADD with a point reference) Excess Deficit • Features of PAO AD anisotropy • One prominent excess region around Centaurus A • One void region near the south pole H.B.K MPLA 28, 1350075 (2013)

  30. Hot spot ? • Features of TA AD anisotropy • No prominent excess region • Broad hot spot • One void region near the north pole

  31. Cen A as a UHECR source H.B.K, ApJ 764, 121 (2013) • Centaurus A is a nearby strong source of radio waves to γ-rays. • The PAO data show the clustering of UHECRs around Centaurus A. M87 Centaurus A contribution + Isotropic background the Cen A fraction the smearing angle Centaurus A • Modeling Centaurus A as a point source of UHECRs

  32. Cen A as a UHECR source Among 69 UHECR observed by PAO,about 10 (6 ~ 17) UHECR can be attributed to Cen A contribution.

  33. Cen A as a UHECR source • Incorporation of Void structure H.B.K, JKPS 62, 708 (2013)

  34. Centaurus A – a UHECR source • Estimate of intergalactic magnetic fields from the deflection angles • By using UHECRs around Centaurus A, the estimate of IGMF is • Without voids – 10 UHECRs • With voids – 18 UHECRs

  35. Composition and GMF Influence • GMF model – Prouza-Smida (2003) model The Galactic plane section of the disk field of the PS model • Lorentz force equation • Fit to observed Faraday rotations • Disk field • Toroidal field • Poloidal field The deflection map of UHECR in the PS model for Z=1 (proton).

  36. Composition and GMF Influence H.B.K, JKPS 63, 135 (2013) The deflections of arrival directions of 69 UHECRs detected by the PAO, due to the GMF, computed using the PS model, when UHECRs are protons (Left), or iron nuclei (Right). Red circles mark the arrival directions detected at the earth, and black bullets connected by yellow lines mark the arrival directions before UHECR enter the GMF .The blue square marks the direction of Centaurus A. • If all UHECRs are protons, the clustering around Centaurus A isnot altered significantly. • If all UHECRs are iron nuclei, the clustering around Centaurus A may be a fake due to the GMF.

  37. Summary • After 100 years of research, the origin of cosmic rays is still an open question, with a degree of uncertainty increasing with energy. • Statistically meaningful data have been accumulated, but not yet conclusive about composition and arrival directions. • Statistical methods to compare two distributions of UHECR arrival directions. • 2D → 1D reduction : CADD • KS or KP test • Point-wise anisotropy and point source search • Centaurus A seems to be a strong source of UHECRs. • Estimate of IGMF : • The influence of GMF may tell something about composition. • Beginning of cosmic ray astronomy?

  38. New Window to the sky Galileo’s telescope Hubble’s telescope Herschel’s telescope Jansky’s radio antenna Tycho’sMural quadrant Penzias & Wilson’s antenna ChandraX-ray telescope Hubble Space Telescope Planck satellite

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